1. Field of the Invention
This invention relates broadly to telecommunications. More particularly, this invention relates to a switching infrastructure and developer environment for telecommunication applications.
2. State of the Art
For much of the history of the telecommunications industry, telephone calls have been connected primarily via the public switch telephone network (PSTN), a point-to-point telecommunications network. The PSTN includes end office (EO) and access tandem (AT) switches. The EO switches connect a local carrier to a subscriber (a party capable of malting or receiving a call), and the AT switches connect local carriers and other intermediary AT switches together. In the PSTN, a path (circuit) is defined between the calling party and the called party through the EO and AT switches, and the call is connected over this path. For a long time, signaling associated with the call (e.g., information about the route through various switches to the called party) and the call content (e.g., analog voice signals) were sent over the same path in the network.
The PSTN was designed to handle voice calls having an average duration of five minutes. Due to a change in calling patterns, in which the average call has become longer, the PSTN network has become quite congested. The reason for the change in calling patterns is, at least in part, a result of the popularity of the Internet and an associated increased data traffic from modem use. Modem calls are typically relatively longer than voice calls, averaging thirty minutes in duration.
As a partial solution to the congestion, the SS7 (signaling system 7) system was deployed. In SS7, the signaling for setting up a path for the call is sent “out-of-band” (over a discrete network), and the call is then connected via a path through the legacy PSTN. While this removes the signaling traffic from the PSTN network switches, even this system does not satisfactorily relieve the PSTN network congestion.
In the 1980's, long distance telecommunication was deregulated. New long distance companies, such as MCI and Sprint, among others, were granted equal access to end-office (EO) switches at the local exchange carrier central office in order to compete directly with AT&T by installing their own access tandem (AT) switches and their own long distance network.
With the Telecommunications Act of 1996, competition was opened for local telephone service, giving rise to competitive local exchange carriers (CLECs). CLECs were permitted equal access to the AT switches of the long distance companies, and local exchanges needed to make space available in their central offices for a competitor's EO switch. As such, the regulatory guidelines that governed the separation of functionalities which previously existed between an AT exchange (switch) and an equal access EO exchange have for the most part diminished. Therefore, switching systems residing in the local exchange today typically have both end-office and access tandem functionality; hence, the term EO/AT.
Given the increase in competition created by deregulation, the cost to the consumer to make a voice call, both local and long distance, has decreased. Consequently, the per call profit to the call provider has also decreased. As such, call providers have been eager to offer profit-making value-added enhanced services above and beyond Class 5 services such as caller-ID, three-way calling, call waiting, etc. Originally, these services were implemented on the EO switches; a typical implementation occurred on the EO switch of the called party. The implementation was “hard coded” into the switch, and a call provider was tied to the EO-switch vendor for services.
It was therefore desired to implement enhanced services in a manner which was both effective and did not rely on the switch vendor for services. To meet this need, the Advanced Intelligent Network (AIN) has been implemented in some areas. The AIN comprises service control points in the SS7 network and operates to move call services away from the traffic switches to de-couple service logic from the switching function and provide an enhanced system of service distribution and third party service suppliers. However, the AIN system has been hindered by SS7 interoperability issues with respect to different Tier 1 International Carriers and also due to vendor-specific implementations. That is, an implementation of the AIN system is confined to a particular geographic area and/or vendor. For example, in Europe there are multiple carriers, each using a different and incompatible AIN protocol.
During the 1990's, the Internet grew at a tremendous rate. Traffic over the Internet is transferred in a uniform manner using Internet Protocol (IP). The IP network therefore has an architecture adapted to provide communication and services over a single and uniformly compatible system worldwide. As such, the IP (or other packet) network has been recognized as a possible substitute for the PSTN.
However, moving from the PSTN system to an IP (or other type of packet) network would require the challenging integration of the IP network with the legacy PSTN system. This is because any change from the PSTN system would necessarily be deployed over time. In addition, the IP network is a packet-based network. This is suitable for viewing web pages on the world-wide web where timing is not critical. It would be ideal to move enhanced call services away from the EO/AT switches and make available and distribute call services in a non-localized manner, similar to the manner in which web pages are made available. Yet, for some call services latency is critical.
Services are distinguished by class, with Class 5 service functions (e.g., three-way calling) requiring practically immediate implementation upon request and therefore residing onboard the stored program control switch (SPCS) in the PSTN. Over the years these embedded service functions have been highly optimized. In fact, it takes only 50-120 milliseconds for an SPCS to route a call to its destination from the time a user goes off-hook and dials the number, inclusive of cycling through a Class 5 feature interaction. This time measurement is referred to as the Class 5 delay budget, and is relatively immovable, as callers expect immediate response for such services. This benchmark poses significant challenges to next-generation telecommunication architecture utilizing an IP network.
When referring to “next-generation” architecture, it is presumed that the application server (AS) which handles the enhanced services will reside separately from the basic call processes (BCP), or call control elements, in the network. Where the AS has been decoupled from a switch, interworking between the decoupled AS and the switch is often implemented using the H.323 Initiation Protocol (SIP). However, there is no evidence that a decoupled AS can be used in a loosely decoupled fashion to implement a Class 5 service in a production network. The Class 5 delay budget imposes an insurmountable barrier to Class 5 service distribution. As such, there is a significant difference between emulation of a Class 5 service in an offline laboratory, and actually replacing a Class 5 end-office switch delivering primary line telephone service to thousands of subscriber lines.
Moreover, once the challenge of integrating the IP and PSTN networks is accepted, it would be further beneficial to have a programming environment which is adapted to facilitate creation, deployment and distribution of enhanced services over the integrated network. Service distribution operates to relieve network congestion. Moreover, service distribution over an IP network reduces the relative high costs associated with using the PSTN for the implementation of such services.
For purposes of this disclosure, the telecommunications network(s) is often referred to using the following suggestive abstract terms: the media transport plane, the signalling and control plane, the application services plane, and the management plane. The media transport plane defines the portion of the network devoted to delivering content from one point (or multipoints) to another point (or multipoints) in the network. The signalling and control plane is primarily used to set up and tear down connections. The application services plane is the portion of the network used to deliver enhanced services. The management plane is used for billing, record keeping, provisioning, etc.
Over the last several years, the efforts of the telecommunications industry to integrate the PSTN with an IP network have been spent largely in proving out the new voice over packet switching technologies which primarily address the media transport plane. To a lesser extent, softswitches, which address the signaling and control plane in the new generation network have just come onto the horizon. This adoption cycle, albeit necessary, has continued at the expense of not realizing any significant advancements in telecommunications service delivery on a large scale during the same time period.